Cryptic glucocorticoid receptor-binding sites pervade genomic NF-κB response elements.

Area of Science:

• Molecular Biology
• Immunology
• Structural Biology

Background:

• Glucocorticoids (GCs) are widely used to treat inflammatory conditions by inhibiting NF-κB signaling.
• The precise mechanism by which the glucocorticoid receptor (GR) represses NF-κB activity is not fully understood.
• Current models suggest GR inhibits NF-κB through protein-protein interactions (tethering) independent of DNA binding.

Purpose of the Study:

• To elucidate the molecular mechanism of GR-mediated repression of NF-κB-driven transcription.
• To investigate the direct interaction between GR and genomic NF-κB response elements (κBREs).

Main Methods:

• Determined five crystal structures of the GR DNA-binding domain (DBD) complexed with κBREs.
• Utilized solution Nuclear Magnetic Resonance (NMR) spectroscopy to analyze GR-κBRE interactions.
• Analyzed the sequence and functional conservation of identified GR binding sites within κBREs.

Main Results:

• Demonstrated direct binding of GR to specific DNA sequences within genomic κBREs.
• Crystal structures revealed GR recognizes a cryptic site between NF-κB subunit binding footprints.
• Identified conserved cryptic sequences across species, indicating an evolutionarily conserved mechanism.

Conclusions:

• GR directly binds to κBREs, mediating the repression of inflammatory gene expression.
• This DNA-binding mechanism provides a new understanding of GR's role in controlling inflammation.
• The findings suggest an evolutionarily conserved strategy for regulating inflammatory responses via GR-κBRE interaction.